The detection of analytes in a liquid (e.g., contaminants in waste water) has numerous useful applications. For example, contaminant monitoring in manufacturing is important when water quality has a direct impact on materials manufactured and when water discharges are monitored for permit compliance. In agriculture, water that was previously directed to disposal by injection could be easily monitored for suitability for crop irrigation. With the ability to quickly detect and monitor major macro and micro minerals of dietary importance, Concentrated Animal Feeding Operations (“CAFO”) programs could be closely monitored to ensure optimum production with minimal waste. Water and waste water management is also important for industries and regulatory bodies involved in energy production and extraction.
Additionally, the revolution in hydraulic fracturing and horizontal drilling methods has made formerly inaccessible oil and gas commercially profitable. These methods depend on the use and management of large quantities of water. The ability to quickly and accurately determine water quality is crucial to modern drilling, fracturing, and oilfield processing of waste streams. Specifically, constituents in water need to be determined for the following reasons:
1. Baseline water quality within the natural aquifers surrounding the potential drilling area need to be determined before any drilling activity takes place and monitored throughout the drilling and production process to ensure no cross contamination of water resources has occurred.
2. Metals (and other inorganic ions) and organic constituents must be compatible with drilling mud chemistries to optimize drilling schedules, reduce maintenance or equipment costs and meet environmental standards while drilling through aquifers.
3. Salt, metal ions, anions (especially borates) and organics must be monitored to optimize gel chemistries for fracturing operations. (Bad fracturing stages caused by unmanaged water quality can cost millions of dollars over the life of a well.)
4. Depending on the geological formation, one recovers between 3 to 11 barrels of water for each barrel of oil—this wastewater must be properly collected, stored and disposed of or optimally reused. The accurate determination of normally encountered metals, anions, microbes and organic constituents (usually coming up from the geological formation) is critical for mixing waste streams, reducing maintenance due to scaling and preventing corrosion of oilfield production and waste storage and transportation assets.
5. Monitoring water constituents is critical for EOR (enhanced oilfield recovery) to maximize hydrocarbon recovery and to prevent damage to the formation (especially when produced and flowback waste waters are utilized).
Critical water monitoring is usually accomplished through a mixture of certified laboratory testing (for initial oilfield chemical development and environmental certifications) and on-site testing for operations and waste water management. On-site chemical testing in the oilfield usually relies on kits and instruments that were originally developed for municipal and well water applications and suffer from the following issues:
1. Most kits suffer from a limited dynamic range requiring time consuming dilutions and the resulting reduction in precision.
2. Many kits are titrimetric and require varying degrees of training and experience to produce reliable results. (Even after one develops the skills to conduct the assay the tests suffer from accuracy issues due to variability caused by the drop counting methods employed.)
3. During the time required for accurate off-site testing cross contamination may substantially impact the fresh water sources.
4. Chemical testing kits also consume a considerable amount of time—dilutions, conducting the tests and clean up between assays often consumes critical time (especially during fracturing operations when analysis speed can prevent failed fracturing stages).
5. Methods that were developed for drinking water aquifers can suffer from interferences that are present in oilfield waters (resulting in lost revenue and problems from poor fracturing stages and plugging of formations and oilfield assets due to inaccurate or absent water testing results). Methods that were developed for monitoring pH suffer from issues that make them inaccurate when conductivities are extremely low or moderately high.
6. Chemical testing kits that use instruments require specialized training and time-consuming reagent handling and calibration steps for proper function.
Rapid, sensitive and on-site water monitoring is also critical for ensuring that waste water discharge meets contractual or environmental limits for agricultural, municipal and industrial runoff requirements as well as a critical step in waste water management.